Rheumatoid arthritis (RA) is a progressive and debilitating disease that often causes hand deformities that impair hand function. A common deformity is at the metacarpophalangeal joints (MCPJs) to cause ulnar drift and extension lag of the fingers. Because of the paucity of high-level evidence studies for RA hand surgical procedures, we began in 2003 a prospective cohort outcomes study to determine the effectiveness of silicone metacarpophalangeal joint arthroplasty (SMPA) procedure for realigning the fingers. This multi- center international study involves the collaboration of rheumatologists and hand surgeons at three comprehensive centers dedicated to the treatment of RA diseases. This current grant follows the world's largest cohort of over 160 RA patients prospectively for 3 years. The short-term (1-year) results have been analyzed for the cohort and have confirmed that the SMPA procedure is highly effective in correcting ulnar drift and improving hand function based on outcomes questionnaire assessments, whereas the medically- treated control group's hand function remains unchanged. The data for year 3 of this project are currently being analyzed. We are proposing to follow this unique cohort for an additional 4 years to assess the long-term outcomes of SMPA, to study the natural history of RA hand disease treated nonoperatively, and to determine predictors of long-term outcomes. This study seeks to define the optimal treatment of this RA hand condition and to provide evidence in guiding hand surgery treatment for this prevalent disease.